This invention is generally related to room air purifiers for use in removing air contaminants such as infectious droplet nuclei, bacteria, smoke, pollen, and dust from the air and particularly to room air purifier assemblies incorporating portable high-efficiency particulate air (HEPA) filters for use in hospital rooms.
HEPA filters, such as that disclosed in U.S. Pat. No. 4,629,482, offer an advantage over other type of filter media in that the amount of airborne pollutants which can be effectively removed from the air is significantly increased. HEPA filters have been defined as filters capable of removing 99.97 percent of airborne particles of the size of 0.3 microns or larger. The filters are designed to maintain higher flow rates (between approximately 150 to 700 cubic feet per minute) than comparable filters, and it has been found that HEPA filters last for longer periods of time and, therefore, offer cost savings to the consumer.
While HEPA filters have been incorporated in room air purifiers in many environments, such as laboratories, scientific research rooms, and even office buildings, there is a particular need for HEPA filtration of airborne particulates in health-care facilities. Specifically, the risk of acquiring tuberculosis in a health-care environment is a function of a concentration of infectious droplet nuclei. Therefore, in such an environment, it is necessary that a room air purifier create an airflow which will circulate all the air within a room through the filter media as often as possible to insure continuous removal of infectious droplet nuclei. The room air purifiers of the prior art have not effectively dealt with this concern.
Another consideration which has not been satisfactorily addressed is the fact that after prolonged use of such purifiers in the hospital environment, the filter elements may accumulate a significant amount of infectious droplet nuclei and become a source of infectious contamination. The prior art has not provided filter housings which adequately prevent accidental contact with filter element(s) contained therein while also allowing easy replacement of such elements.
Another consideration which has not been satisfactorily dealt with by prior art mobile room air purifiers is that they have been made light weight and compact for domestic use and, as such, do not separate the air inlet and air outlet to the extent necessary to provide the air velocity and circulation patterns required for the rapid capture of particulates, including pathogenic microorganisms which are generated by a patient.
Another consideration which has not been appreciated by prior art room air purifiers is the need to make the units as quiet as possible. Many, if not all, of HEPA filter room air purifiers utilize blowers or fans which are noisy during operation. This can be quite irritating to health-care patients who are in need of rest.